"I allowed that ten years sounded fine to me. I continue to hear similar sentiments from HBO every time I have a meeting with them, be it in LA or New York," Martin wrote.

Executive producers David Benioff and D. B. Weiss have said they'd like to see the series wrap up in seven seasons. The show's fifth season premieres April 12, with HBO giving the show a strong vote of confidence by ordering a sixth season along with season five. The castmembers are signed on through season seven. Martin says all the speculation in the world won't mean anything until next year, during season six.

"Around the time that the second episode of season six is showing, HBO will order season seven, we hope... or maybe, just maybe, they will order seasons seven AND eight," wrote Martin. "But even if they just order season seven, that doesn't mean that the show will end in seven; it could just represent a return to the original policy of committing to only one season at a time."

Martin also addressed speculation that the series could be concluded with a theatrically released film (or films), a notion he himself has discussed before. Thrones already became the first TV series to screen on IMAX earlier this year, with a limited showing of episodes nine and ten of season four.

"Sure, I love the idea. Why not? What fantasist would not love the idea of going out with an epic hundred million feature film?" Martin wrote. "And the recent success of the IMAX experience shows that the audience is there for such a movie. If we build it, they will come. But will we build it? I have no bloody idea."

Martin is currently working on the sixth book in a planned seven book series in A Song of Ice and Fire series, which Thrones is based upon.

"Seven seasons, ten seasons, with or without one or two feature films... in the end, all that matters is that we tell a great story, with a great end," Martin wrote.